About installation issues, just to share my experience : 2 days after I installed it, I still couldn't launch this game (It was before the patch and forums were a mess).
Until I :
_closed steam
_erased every content in AppData/Roaming/CreativeAssembly/Rome 2
_reinstalled vcredist by clicking on the exe in Rome 2 main folder
_cleaned a bit with CCCleaner
_launched steam, but not automatically, as advised on steam support : I disconnected from my account, and then connected again by entering my account name and password
Hope it's clear since english isn't my mother tongue. I'm not sure that every step is so important except vcredist reinstallation, maybe the cleaning of appdata file and the way to reconnect on ones steam account that (it might reboot something in the steamapp).